Refering to Wikipedia the word Prototype is defined as follows:

A prototype is an early sample, model or release of a product built to test a concept or process or to act as a thing to be replicated or learned from.³⁾

In this section reasons for the importance of prototyping are given as well, as an argumentation if and how the terms sketch and prototype can be distinguished.

Tim Brown, president of IDEO once said:

„Never go to a meeting without a prototype at whatever stage of development, one week, one month, six months“ ⁴⁾

The autors Tom Kelly (partner of IDEO) and David Kelly (founder of IDEO) state in their article Why Designers Should Never Go to a Meeting Without a Prototype the same opinion like Brown. They reason that a prototype is an embodiment of an idea which can help to convince bosses or key stakeholder when words alone will not. In their point of view the major goal of prototyping is experimentation. It enables designers to try out different approaches, so called low-cost experiments, to find problems and failures quick, cheap and early and gives them the time and ressources needed to iterate and optimize their ideas multiple times.

Side note: There exists a highly interesting TED talk of Tim Brown about Tales of creativity and play. This is not directly related to prototyping, but if you are interested in the man behind the quote mentioned above, take a look!

A good example for the communication of ideas via different prototypes is a project from the company Intuity. They developed an Entertainmentsystem for cars commisioned by the Daimler AG. Therefore the following three prototypes were created:

• Concept Movie:
  To help superiors evaluate the business potential of the project.
  
  
• Interactive Flash and Arduino Prototype:
  To evaluate the systems acceptance by potential users. Very fast creation of different variants of the prototype, with respect to users needs possible.
  
  
• Use of a Testing-car and Final Hardware:
  To give engineers the possibility to detect technical problems early and develop solutions.
  

Another example from Tom and David Kelly´s article is the story of a toy inventor (Adam Skaates) and gaming expert (Coe Leta Stafford), who created a low-tech prototype for an Iphone-App feature in only one hour. To illustrate their idea off an elmo figure which reacts on touch gestures with wild movements as part of a game for children, they used a simple printed Iphone frame. Inside the frame stood Adam Skaates and acted as elmo, while his colleague used her hand to simulate the touch gestures on the elmo figure. After recording the scenario they had a fun and interactive video which they showed to the Sesame Workshop team in a meeting. The meeting took place just a few minutes after they finished their preparation. Today the idea is present in the app Elmo´s Monster Maker which can be downloaded from the ITunes store.

Refering to Fred Nickols article Prototyping: Systems Development in Record Time it is possible to simplify, speed up and reduce the costs of development throughout the use of prototypes.

The company Intuity was with the help of prototypes enabled to highly reduce the time needed for the development of a novel eMobility Ecosystem. It was possible for them to react quickly on changes and arrising obstacles, as well as having a continuous overview on the work progress.

Again multiple prototypes were created. At first they developed different Use-Cases for the european as well as the market in far eastern countries. In the next step they created paper prototypes to simulate the softwares user interface. To model the infrastructure of the eMobility charge stations, they used different prototyping techniques. To determine a fitting form, static physical real life sized cardboard models followed by CNC milled ones were created. These casings got afterwards equipped with screens and Arduino boards to evaluate user interactions and experiences.

Intuity does not only see a temporal benefit in prototyping, but argues that it also increases the feeling of security for all parties involved. This is due to a shrinking risk of development into the wrong direction, when iteratively creating different prototypes.

Every designer is familiar with the so called napkin sketch, which implicates the simple drawing of a first design idea on a piece of paper one has lying around. But can this sketch already be considered a prototype? Refering to Krug ⁵⁾, at least it is already possible to evaluate such a drawing with very simple testing. On the other hand a testing of such an interface differs highly from the evaluation of an interactive physical prototype, which can be touched and directly manipulated.

Buxton ⁶⁾ says that sketches and prototypes are clearely two different things and separates them by their properties.

Refering to Mousette ^{7) 8)}, in general sketching and prototyping are closely related to each other. He argues that Buxtons polarization can be useful to understand the general differences between the two, but sees the real distinction in a systems target group and the way of creation a sketch or prototype originated from. He defines the two terms as follows:

• Sketch:
  When using sketches, ideas and different design variants get created in small iterations with the use of different materials (e.g. pen and paper, programming code, electronics, digital or analoge tools). Sketches make it possible to quickly develop new ideas and find solutions for existing problems. A designer or the autor himself are in most cases the target group of the final result.

• Prototype:
  A prototype is a combination of different ideas, having the goal to make these experienceable for others. Its values and qualities can be mediated implicit or explicit. Prototypes can be understood by people unrelated to a specific field. Their major target group is the environment, consisting out of employees, the public, members of a specific community and many more.

Mousette also argues that prototyping can be seen as a Learning by Doing process. Du to him it is extremely important to begin the creation of prototypes already when starting a new project to familiarize with the related materials and technologies. In his oppinion, this can help forseeing future problems which can arise during the design phase and avoids that a project develops to far in the wrong direction. Mousette describes two approaches which can be used when starting a new project:

• Theoretic Approach:
  Try to understand everything by analysis and discover the relationships between parts of the project.

• Practical Approach:
  Build everything that is given and try to understand it by doing.

He further states that prototyping is beneficial for designers, while new materials and technologies which allow new concepts and qualities can be discovered.

There are various forms of prototypes, like static and interactive software prototypes, or static and interactive physical prototypes (hardware sketches). Although, the focus of this article lays on physical prototyping (static as well as interactive), anotations and references to software prototyping will be given when deemed appropriate. In the following static and interactive prototyping will be distinguished and the two interactive physical prototyping forms Design-Prototype and Engingeering-Prototype will be introduced.

In the article Using Prototypes to Improve UI Design the difference between static and interactive software prototyping is elucidated.

The above shown images illustrate static software prototyping (left image) and interactive software prototyping (right image), whichs distinction is closely related to the one of its physical counterparts. The difference is like follows:

• Static Prototype:
  Like displayed in the left graphic, in static software prototyping no interactions with an object can be executed. They can only be described and have to be imagined by the recipient (e.g. a candidate for an usability-test). The same applies to static physical prototypes, with the difference that they can in contrast to the software pendant be touched and held in hand. Static physical prototypes can be produced in multiple different shapes and compared with each other. A good example are the rotary knobs of the HaptICS – Haptic Interface Comunication System from nui lab.
  
  
  The knobs alone, without beeing used for interactions are already static physical prototypes. They transform to an interactive prototype when beeing enhanced with further technical components to manipulate some kind of interface. Another example are the cardboard models which were used in the quick development of an eMobility Ecosystem.

• Interactive Prototype:
  In contrary to the static prototype, in the right image above a user is shown actively using a system during an usability-test. Due to this not only feedback for a systems visual look, but for its interactive behaviour can be collected. This also applies to interactive hardware sketches, while they enable designers to test reality and build a base for decision making during the design process. The development process of the augumented-reality-presentation "Magic and Storytelling" which was created for a TED talk held by Marco Tempset gives a good example for an interactive prototype. Another example was presented in the second prototype for the already mentioned car Entertainmentsystem.

Techniques and toolkits which can help creating this types of prototypes will be introduced later.

Generally there are multiple ways to divide all kinds of Prototypes into categories ^{9) 10)}. In the following section specifically the two forms Design-Prototype and Engineering-Prototype in which interactive physical prototypes can be separated regarding to Jan Barth et al. ¹¹⁾ will be introduced:

• Design-Prototype:
  Presenting a complex design idea to stakeholders can become problematic if only paper sketches and drawings are given. Especially if the concept includes animations, the audience might has difficulties to understand it or imagine the final product without seeing it. To prevent this from happening and present ideas already during early development stages in a more visual and interactive way it is possible to build a physical Design-Prototype. This one consists of a simple programm which can be implemented in a fast and low cost way, using one or multiple of the tools, techniques and frameworks.To further speed up the creation it can make sense to reuse already existing code, either from previous projects or Opensource-Community-Plattforms like e.g. openprocessing or the Arduino - User Code Library. The car Entertainmentsystem project included the use of Design-Prototypes.

• Engineering-Prototype:
  The purpose of an Engineering-Prototype is to demonstrate the technical operability and verify the operational stability of hardware-sketches, created using new technologies or pieces of hardware. For lately launched technological products (e.g. Microsoft Kinect (v2)) it might be the case that no previous experiences are available. When using them one needs to develope solutions for connection and implementation in a working prototype by himself. The resulting creations can be considered an experiment from which designers can gain experiences for later implementations in final products. While good structured programming is less important in Design-Prototypes it plays a major role in Engineering-Prototypes. To keep the possibilities of deployment as flexible as possible it is crucial to work generic and modular.

Although, there is a huge variety of toolkits and techniques for different prototyping tasks available, no solution covers every domain. This section introduces a toolkit-advisor-framework which helps users to find a prototyping toolkit, not only fitting their project, but their personal level of experiences as well. Afterwards different available toolkits and techniques will be listed and briefly described.

Reggarding to Kowalski ¹²⁾ which toolkit to use does not only depend on the project at hand, but also on the employees processing it. He developed a framework which aids the resolution of the following problems:

• Amount of Toolkits:
  There are numerous different prototyping toolkits available, which makes the right selection difficult. Additionaly there is not in every case enough information about their degree of „powerfulness“ given.
  
  
• Entry barriers:
  Different toolkits have different levels of entry barriers. It is possible that a toolkit with a high barrier fits perfectly for use in a project, but the developers skill level is to low.

Kowalskis framework represents a structuring of available toolkits in two steps. First he separated the broad field of different toolkit-users into the four unique user profiles Apprentice, Explorer, Master and Do-It-Yourself-Guy, which describe their levels of knowledge and expectations. Second he gives further aspects on how to differentiate currently available prototyping toolkits. These include Available Components, Mightiness, Beginner-friendly, Location of power supply, Location of processing power, Programming language support and Platform independency.

The framework is displayed as a two dimensional graph, which is divided in four categories to hold the four user profiles, by a two by two matrix. The graphs x-axis represents the beginner-friendliness, while the y-axis corresponds to the amount of available toolkit components, which is directly linked to the toolkit´s mightiness. A graphical representation of the framework can be seen below.

Since the hole range of available prototyping toolkits and techniques is extremely large, there will only the ones deemed most important or interesting beeing introduced in detail. They are divided into the two categories static physical prototyping and interactive physical prototyping toolkits and techniques. Of course at the bottom of this section, additional references to other toolkits will be given.

Toolkit: Arduino
	Arduino Uno: The Arduino Uno was collaboratively developed from the Interaction Design Institute Ivrea (school is closed) and the Tisch School of the Arts at New York University. The microcontroller plattform consists out of open-source electronics and is based on easy to use hard- and software.13) An Arduino board can easily enhanced with so called shields. Current Price Shields Sensors
	Arduino Starter-Kit: This kit already contains a variety of sensors and additional components. A list of all included parts can be found here. Current Price
	Arduissimo: The Arduissimo is a current project (state 05/13/14) presented on the platform Indiegogo. Its goal is to build an Arduino plattform which supports 16 cores and enables a better use of virtual peripherals (hardware simulations) on Arduino Boards. Although this devices encourages virtual prototyping, it can be beneficial for designers to beeing enabled to combine the virtualization of hardware parts and the use of physically existing sensors. Current Price
	Software-Programming-Environments: Arduino Software Development Tools VVVV Processing Firefly
	Tutorials: Arduino.cc Adafruit.com Exploringarduino.com Tronixstuff.com Arduino-tutorial.de Ladyada.net
	Literature: Manuals and Curriculum (Arduino.cc) The 5 best Arduino Books (engblaze.com) Introduction to Arduino, Alan G. Smith (princeton.edu) Prototyping Interfaces - Interaktives Skizzieren mit vvvv 14)

Toolkit: Lego Mindstorm
	Lego Mindstorm: The Mindstorm Toolkit, uses lego blocks, attacheable sensors and a central microcontroller for the construction of prototypes. The central unit, which is called NXT, provides a display screen and a speaker for output. Further outputdevices (e.g. servo motors) and inputdevices (e.g. color, touch or light sensors) can be wired to the NXT. Current Price
	Software-Programming-Environments: Mindstorm Software NXT Programms
	Tutorials: legoengineering.com Stemcentric.com Drgraeme.net Ortop.org (Essential Tutorial) Ortop.org (Advanced Tutorial)
	Literature: LEGO MINDSTORMS EV3 Laboratory, Daniele Benedettelli The art of Lego Mindstorms NXT-G programming, Terry Griffin The unofficial guide to Lego Mindstorm Robots, Jonathan B. Knudson Winning Design Lego Mindstorms NXT, James J. Trobaugh Lego Mindstorms NXT-G Programming Guide, James Floyd Kelly

Toolkit: Gainer
	Gainer: This toolkits environment is useful for education (users can learn by mistake) as well as actuall installations. It consist of a breadboard which can be enhanced with so called bridge modules, through which the capabilities of I/O-Ports can be expanded. Unfortunately the handling can be problemativ for unexperienced users, since at least basics for working with electronics are required and the official toolkits website is partially japanese only. The hard- and software is, equal to the Arduino project, open-source. Current Price
	Software-Programming-Environments: Gainer Software & Drivers MAX/MSP Library Processing Library Flash Library
	Tutorials: gainer.cc (Assembling) gainer.cc (Gainer and Max/MSP) gainer.cc (Gainer and Flash)
	Literature: Physical Computing with Gainer (japanese only)

Toolkit: Phidgets
	Phidgets: The so called phidgets are a set of building blocks which can be connected to a computer via USB. With the use of them it is possible to explore alternatives for physical interaction with computer systems, while easily attaching or disconnecting them. An advantage of Phidgets is, that developers are not bound to a specific programming language, but can use their prefered due to a broad support of different ones. I/O Boards Sensors Motors
	Software-Programming-Environments: Drivers & Libraries
	Tutorials: phidgets.com (Phidgets and java) Phidgets and MAX/MSP sockeye.cs.washington.edu cycling74.com grouplab.cpsc.ucalgary.ca

Further Toolkits and Information can be found at the following websites:

Toolkits:

• sketchinginhardware.com
• Prototyping in Physical Computing - Sketching in Hardware, Robert Kowalski

Information:

• generationrobots.com
• Other physical computing platforms (morecatlab.akiba.coocan.jp)

Recent commonly used computer interfaces only exploit few of the human bodies abilities to interact with a system. With only offering input devices like mouses, keyboards or touchdisplays, still multiple sensoring capabilities of humans stay unused. This problem was illustrated in an interesting way by Dan O’Sullivan and Tom Igoe ¹⁵⁾ with their finger-eye-beeing a decade ago. They tried to show the limitation of body sensor capabilities which humans could use at that time time to communicate with an electronic system. Their eyes, ears and fingers where the only body sensors used at that time. ¹⁶⁾

The search for alternative ways of communcation already started in the past. Research projects with the purpose of using objects for communication with computer interfaces, were conducted. They resulted in Tangible-User-Interfaces (TUIs) which allow users to control virtual objects with physical ones, depending on their context. These hardware interfaces integrate not only the human visual sense, but the ability of haptical perception as well.

Todays Tangible-User-Interfaces are no longer static physical objects, but can transform the haptic experience they have on a user during runtime. Throughout this it is possible to change an objects haptic-signal dynamical, depending on its context (e.g. location of the object). This enables new usage scenarios in the field of Human-Computer-Interaction (HCI). On the other hand the question arises, what the right way of applying this haptic feedback is, so that it feels natural to the user. What is the right balance between new technologies and an objects normal physical behaviour a user is used to?

To find a solution for this problem, users could in theory just be asked what kind of haptic feedback they like. Unfortunately it is difficult for humans to verbalize their haptic perceptions in a precise and clear way, due to a lack of vocabulary. To avoid this problem, designers created in the past single prototypes for the desired hardware to be tested by users. Due to this, long breaks between two prototypes existed, which made the design process slow and indirect. A solution for this problem is the use of a modular prototyping toolkit, which allows users to receive haptic feedback, simultaneously manipulate it and switch between different representations of the same object.

An example for such a toolkit is the already in the section Static vs. Interactive Prototyping introduced HaptICS – Haptic Interface Comunication System.

Although there were already some examples for physical prototyping introduced within the article, Marco Tempsets project about Magic and Storytelling as well as the BMW Kinetic were not presented in detail, yet. Since these two are particularly interesting illustration they will be shown in this section. At the sections end further examples will be listed.

Marco Tempsets "Magic and Storytelling" project, developed by Onformative, was already mentioned in the section Static vs. Interactive Prototyping. In the following we will give a more detailed insight to the creation process of the Augumented-Reality-Presentation. The special thing concerning this project is, that not only for the preperation of the show prototyping was used, but that the result itself was a hardware-sketch as well. The aim of the project was to create a realtime AR-Show in HD-Quality in which generated objects fly around marco temporally connected to an audio play-back.

To verify the feasibility of the project, the team from Onformative created a few Engineering-Prototypes in Openframeworks, before starting the implementation. These included the following two prototypes:

• 3D-Compositing:
  This prototype was determined to evaluate the possibility of positioning a person inside a room, so that live generate AR-Elements fly around him/her.

• Face-Substitution:
  It was based on a library from Jason Saragih tested, if Marco Tempsets face could be substituted in a stable way.

Later parts of the show were created in collaboration with checksum5 in vvvv. The use of vvvv had multiple advantages:

• Always running:
  Patches created in vvvv can be manipulated within runtime. While most objects in the show were created live it was also necessary to design live.

• Variety of Interfaces:
  The huge amount of devices (e.g. Microsoft Kinect) which can be connected to vvvv was a further advantage during the projects development.

• Timeline:
  Vvvv includes a timeline which was due to the deployment of time-bound effects of great help.

To determine the look and behavior of a particlesystem flying around in the air, Design-Prototypes with the help of Processing were created. While tracking Marco Tempsets hands it was possible to let particles appear at the locations of his hands and also move them related to his hand. The used programming environment Processing has good properties for the creation of fast digital sketches. It is compared to other products quite simple and has a broad support consisting out of multiple libraries, tutorials and code samples. On the other hand it has its limits, when the code gets to complex or real-time applications are required.

There is also a behind the scences video available.

The development process of the kinetic sculpture displayed in the BMW museum, which was created by the ART+COM AG gives a good example of physical prototyping. According to Ängelslevä (creative director ART+COM AG), they built a hardware prototype of the sculpture to convince BMW that the effort of implementing the system is worth it.

They used a cabin with 25 metal balls hanging on wires. Each of the balls could be lifted up and down by an individually controllable stepper motor. The prototype allowed them to simultaneously test the esthetics of the balls movement in the 3 dimensional matrix and at the same time go on with the design process. Eventually the hardware prototype was combined with a software simulation to make the experience for the viewers even more intense.

Further examples for hardware sketches can be found when following the links in the Sources of Inspiration page or on the following websites:

• Arduino Patches (Arduino.cc)
  
• Arduino Patches (Intel.com)
  

There are several different Conferences conerning prototyping:

• Sketching in Hardware Series (e.g. Video 2012)
• RAPID
• Advanced Research in Virtual and Rapid Prototyping

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